Network throughput: Difference between revisions

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The '''asymptotic throughput''' (less formal ''asymptotic bandwidth'') for a packet-mode [[communication network]] is the value of the [[maximum throughput]] function, when the incoming network load approaches [[infinity]], either due to a [[Message passing|message size]] as it approaches [[infinity]],<ref>''Modeling Message Passing Overhead'' by C.Y Chou et al. in Advances in Grid and Pervasive Computing: First International Conference, GPC 2006 edited by Yeh-Ching Chung and José E. Moreira {{ISBN|3540338098}} pages 299-307</ref> or the number of data sources is very large. As other [[bit rate]]s and [[data bandwidth]]s, the asymptotic throughput is measured in [[bits per second]] (bit/s), very seldom [[byte]]s per second (B/s), where 1 B/s is 8 bit/s. [[Decimal prefix]]es are used, meaning that 1 Mbit/s is 1000000 bit/s.

Asymptotic throughput is usually estimated by sending or [[network simulation|simulating]] a very large message (sequence of data packets) through the network, using a [[greedy source]] and no [[flow control (data)|flow control]] mechanism (i.e., [[User Datagram Protocol|UDP]] rather than [[Transmission Control Protocol|TCP]]), and measuring the network path throughput in the destination node. Traffic load between other sources may reduce this maximum network path throughput. Alternatively, a large number of sources and sinks may be modeled, with or without flow control, and the aggregate maximum network throughput measured (the sum of traffic reaching its destinations). In a network simulation model with infinite packet queues, the asymptotic throughput occurs when the [[latencyNetwork (engineering)latency|latency]] (the packet queuing time) goes to infinity, while if the packet queues are limited, or the network is a multi-drop network with many sources, and collisions may occur, the packet-dropping rate approaches 100%.

A well known application of asymptotic throughput is in modeling [[point-to-point communication]] where (following Hockney) [[latency (engineering)|message latency]] T(N) is modeled as a function of message length N as T(N) = (M + N)/A where A is the asymptotic bandwidth and M is the half-peak length.<ref>''Recent Advances in Parallel Virtual Machine and Message Passing Interface'' by Jack Dongarra, Emilio Luque and Tomas Margalef 1999 {{ISBN|3540665498}} page 134</ref>